Merge branch 'mlx5-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mellanox/linux

Saeed Mahameed says:

====================
mlx5-next auxbus support

This pull request is targeting net-next and rdma-next branches.

This series provides mlx5 support for auxiliary bus devices.

It starts with a merge commit of tag 'auxbus-5.11-rc1' from
gregkh/driver-core into mlx5-next, then the mlx5 patches that will convert
mlx5 ulp devices (netdev, rdma, vdpa) to use the proper auxbus
infrastructure instead of the internal mlx5 device and interface management
implementation, which Leon is deleting at the end of this patchset.

Link: https://lore.kernel.org/alsa-devel/20201026111849.1035786-1-leon@kernel.org/

Thanks to everyone for the joint effort !

* 'mlx5-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mellanox/linux:
  RDMA/mlx5: Remove IB representors dead code
  net/mlx5: Simplify eswitch mode check
  net/mlx5: Delete custom device management logic
  RDMA/mlx5: Convert mlx5_ib to use auxiliary bus
  net/mlx5e: Connect ethernet part to auxiliary bus
  vdpa/mlx5: Connect mlx5_vdpa to auxiliary bus
  net/mlx5: Register mlx5 devices to auxiliary virtual bus
  vdpa/mlx5: Make hardware definitions visible to all mlx5 devices
  net/mlx5_core: Clean driver version and name
  net/mlx5: Properly convey driver version to firmware
  driver core: auxiliary bus: minor coding style tweaks
  driver core: auxiliary bus: make remove function return void
  driver core: auxiliary bus: move slab.h from include file
  Add auxiliary bus support
====================

Link: https://lore.kernel.org/r/20201207053349.402772-1-saeed@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 235 insertions, 0 deletions

diff --git a/Documentation/driver-api/auxiliary_bus.rst b/Documentation/driver-api/auxiliary_bus.rst
new file mode 100644
index 000000000000..2312506b0674
--- /dev/null
+++ b/Documentation/driver-api/auxiliary_bus.rst
@@ -0,0 +1,234 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+=============
+Auxiliary Bus
+=============
+
+In some subsystems, the functionality of the core device (PCI/ACPI/other) is
+too complex for a single device to be managed by a monolithic driver
+(e.g. Sound Open Firmware), multiple devices might implement a common
+intersection of functionality (e.g. NICs + RDMA), or a driver may want to
+export an interface for another subsystem to drive (e.g. SIOV Physical Function
+export Virtual Function management).  A split of the functinoality into child-
+devices representing sub-domains of functionality makes it possible to
+compartmentalize, layer, and distribute domain-specific concerns via a Linux
+device-driver model.
+
+An example for this kind of requirement is the audio subsystem where a single
+IP is handling multiple entities such as HDMI, Soundwire, local devices such as
+mics/speakers etc. The split for the core's functionality can be arbitrary or
+be defined by the DSP firmware topology and include hooks for test/debug. This
+allows for the audio core device to be minimal and focused on hardware-specific
+control and communication.
+
+Each auxiliary_device represents a part of its parent functionality. The
+generic behavior can be extended and specialized as needed by encapsulating an
+auxiliary_device within other domain-specific structures and the use of .ops
+callbacks. Devices on the auxiliary bus do not share any structures and the use
+of a communication channel with the parent is domain-specific.
+
+Note that ops are intended as a way to augment instance behavior within a class
+of auxiliary devices, it is not the mechanism for exporting common
+infrastructure from the parent. Consider EXPORT_SYMBOL_NS() to convey
+infrastructure from the parent module to the auxiliary module(s).
+
+
+When Should the Auxiliary Bus Be Used
+=====================================
+
+The auxiliary bus is to be used when a driver and one or more kernel modules,
+who share a common header file with the driver, need a mechanism to connect and
+provide access to a shared object allocated by the auxiliary_device's
+registering driver.  The registering driver for the auxiliary_device(s) and the
+kernel module(s) registering auxiliary_drivers can be from the same subsystem,
+or from multiple subsystems.
+
+The emphasis here is on a common generic interface that keeps subsystem
+customization out of the bus infrastructure.
+
+One example is a PCI network device that is RDMA-capable and exports a child
+device to be driven by an auxiliary_driver in the RDMA subsystem.  The PCI
+driver allocates and registers an auxiliary_device for each physical
+function on the NIC.  The RDMA driver registers an auxiliary_driver that claims
+each of these auxiliary_devices.  This conveys data/ops published by the parent
+PCI device/driver to the RDMA auxiliary_driver.
+
+Another use case is for the PCI device to be split out into multiple sub
+functions.  For each sub function an auxiliary_device is created.  A PCI sub
+function driver binds to such devices that creates its own one or more class
+devices.  A PCI sub function auxiliary device is likely to be contained in a
+struct with additional attributes such as user defined sub function number and
+optional attributes such as resources and a link to the parent device.  These
+attributes could be used by systemd/udev; and hence should be initialized
+before a driver binds to an auxiliary_device.
+
+A key requirement for utilizing the auxiliary bus is that there is no
+dependency on a physical bus, device, register accesses or regmap support.
+These individual devices split from the core cannot live on the platform bus as
+they are not physical devices that are controlled by DT/ACPI.  The same
+argument applies for not using MFD in this scenario as MFD relies on individual
+function devices being physical devices.
+
+Auxiliary Device
+================
+
+An auxiliary_device represents a part of its parent device's functionality. It
+is given a name that, combined with the registering drivers KBUILD_MODNAME,
+creates a match_name that is used for driver binding, and an id that combined
+with the match_name provide a unique name to register with the bus subsystem.
+
+Registering an auxiliary_device is a two-step process.  First call
+auxiliary_device_init(), which checks several aspects of the auxiliary_device
+struct and performs a device_initialize().  After this step completes, any
+error state must have a call to auxiliary_device_uninit() in its resolution path.
+The second step in registering an auxiliary_device is to perform a call to
+auxiliary_device_add(), which sets the name of the device and add the device to
+the bus.
+
+Unregistering an auxiliary_device is also a two-step process to mirror the
+register process.  First call auxiliary_device_delete(), then call
+auxiliary_device_uninit().
+
+.. code-block:: c
+
+	struct auxiliary_device {
+		struct device dev;
+                const char *name;
+		u32 id;
+	};
+
+If two auxiliary_devices both with a match_name "mod.foo" are registered onto
+the bus, they must have unique id values (e.g. "x" and "y") so that the
+registered devices names are "mod.foo.x" and "mod.foo.y".  If match_name + id
+are not unique, then the device_add fails and generates an error message.
+
+The auxiliary_device.dev.type.release or auxiliary_device.dev.release must be
+populated with a non-NULL pointer to successfully register the auxiliary_device.
+
+The auxiliary_device.dev.parent must also be populated.
+
+Auxiliary Device Memory Model and Lifespan
+------------------------------------------
+
+The registering driver is the entity that allocates memory for the
+auxiliary_device and register it on the auxiliary bus.  It is important to note
+that, as opposed to the platform bus, the registering driver is wholly
+responsible for the management for the memory used for the driver object.
+
+A parent object, defined in the shared header file, contains the
+auxiliary_device.  It also contains a pointer to the shared object(s), which
+also is defined in the shared header.  Both the parent object and the shared
+object(s) are allocated by the registering driver.  This layout allows the
+auxiliary_driver's registering module to perform a container_of() call to go
+from the pointer to the auxiliary_device, that is passed during the call to the
+auxiliary_driver's probe function, up to the parent object, and then have
+access to the shared object(s).
+
+The memory for the auxiliary_device is freed only in its release() callback
+flow as defined by its registering driver.
+
+The memory for the shared object(s) must have a lifespan equal to, or greater
+than, the lifespan of the memory for the auxiliary_device.  The auxiliary_driver
+should only consider that this shared object is valid as long as the
+auxiliary_device is still registered on the auxiliary bus.  It is up to the
+registering driver to manage (e.g. free or keep available) the memory for the
+shared object beyond the life of the auxiliary_device.
+
+The registering driver must unregister all auxiliary devices before its own
+driver.remove() is completed.
+
+Auxiliary Drivers
+=================
+
+Auxiliary drivers follow the standard driver model convention, where
+discovery/enumeration is handled by the core, and drivers
+provide probe() and remove() methods. They support power management
+and shutdown notifications using the standard conventions.
+
+.. code-block:: c
+
+	struct auxiliary_driver {
+		int (*probe)(struct auxiliary_device *,
+                             const struct auxiliary_device_id *id);
+		void (*remove)(struct auxiliary_device *);
+		void (*shutdown)(struct auxiliary_device *);
+		int (*suspend)(struct auxiliary_device *, pm_message_t);
+		int (*resume)(struct auxiliary_device *);
+		struct device_driver driver;
+		const struct auxiliary_device_id *id_table;
+	};
+
+Auxiliary drivers register themselves with the bus by calling
+auxiliary_driver_register(). The id_table contains the match_names of auxiliary
+devices that a driver can bind with.
+
+Example Usage
+=============
+
+Auxiliary devices are created and registered by a subsystem-level core device
+that needs to break up its functionality into smaller fragments. One way to
+extend the scope of an auxiliary_device is to encapsulate it within a domain-
+pecific structure defined by the parent device. This structure contains the
+auxiliary_device and any associated shared data/callbacks needed to establish
+the connection with the parent.
+
+An example is:
+
+.. code-block:: c
+
+        struct foo {
+		struct auxiliary_device auxdev;
+		void (*connect)(struct auxiliary_device *auxdev);
+		void (*disconnect)(struct auxiliary_device *auxdev);
+		void *data;
+        };
+
+The parent device then registers the auxiliary_device by calling
+auxiliary_device_init(), and then auxiliary_device_add(), with the pointer to
+the auxdev member of the above structure. The parent provides a name for the
+auxiliary_device that, combined with the parent's KBUILD_MODNAME, creates a
+match_name that is be used for matching and binding with a driver.
+
+Whenever an auxiliary_driver is registered, based on the match_name, the
+auxiliary_driver's probe() is invoked for the matching devices.  The
+auxiliary_driver can also be encapsulated inside custom drivers that make the
+core device's functionality extensible by adding additional domain-specific ops
+as follows:
+
+.. code-block:: c
+
+	struct my_ops {
+		void (*send)(struct auxiliary_device *auxdev);
+		void (*receive)(struct auxiliary_device *auxdev);
+	};
+
+
+	struct my_driver {
+		struct auxiliary_driver auxiliary_drv;
+		const struct my_ops ops;
+	};
+
+An example of this type of usage is:
+
+.. code-block:: c
+
+	const struct auxiliary_device_id my_auxiliary_id_table[] = {
+		{ .name = "foo_mod.foo_dev" },
+		{ },
+	};
+
+	const struct my_ops my_custom_ops = {
+		.send = my_tx,
+		.receive = my_rx,
+	};
+
+	const struct my_driver my_drv = {
+		.auxiliary_drv = {
+			.name = "myauxiliarydrv",
+			.id_table = my_auxiliary_id_table,
+			.probe = my_probe,
+			.remove = my_remove,
+			.shutdown = my_shutdown,
+		},
+		.ops = my_custom_ops,
+	};
diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
index f357f3eb400c..86759a74b7f1 100644
--- a/Documentation/driver-api/index.rst
+++ b/Documentation/driver-api/index.rst
@@ -72,6 +72,7 @@ available subsections can be seen below.
    thermal/index
    fpga/index
    acpi/index
+   auxiliary_bus
    backlight/lp855x-driver.rst
    connector
    console